Incandescent lamp



May 7, 1929. L. J. vooRl-IEES v INCANDESCENT LAMP 2 sneetssheet l Filed May 27 1921 May 7, 1929. 1 J. vooRHEx-:s

INCANDESCENT L/AMP L lll ly having the atented May 7, 1929.

` il. WORHEES,

Ol? BINGHAMTON, NEW YORK, ASSIGNOR T NATIONAL CARBON CllPAlll'Y, NG., A COLlLPRATION 0F NEW YORK.

INGANDESCENT LAMP.`

Application filed May 27,

Vlhis invention relates to illuminating devices having an incandescent lamp adjustably mount-ed within a reflector. i

lin devicesot this lrind, the adjustment is provided to enable the user to place the lamp directly in focus, or to shift its position relative to the focus so as to modify the character o' the illurnination obtained. liauipbulbs, reflectors andiholders are :ordinarily so made that, when of standardsize, the lamp lilainent is properly positioned at the focus ot the reflector. But owing to unavoidable variation in manufacture, it frequently happens that one or more of the assembled meinbers deviate from the standard in such inanner that proper focus cannot be obtained, unless means are provided 'tor relative adliustincnt. A further advantage of adjustability is that an illuminating device is made adaptable tor varied service requirements when its light may be concentrated in a narrow, powerful beam or diiiused te illuminate adequately a relatively large` area. y

The advantages to be obtained from focusing devices have been impaired in prior structures by reason of the extreme compactness of the lamp filament. ln the endeavor to obtain an illuininant concentrated .much as possible at the focus of the rel'lector, usualliorm of a parabola `of revolution, the incandescent lila-:nent has been itoruied into a spiral or otherwise contracted to a tcw one-hundredths ot an inch in diu mensions. ll: positioned exactly at the locus ot the parabola, such filament-s give a cmicentrated beam. of light, but are not capable ol' adjustment to give a satisfactory dif- 'tused illumination. lliis is due to 'the fact that il' the lamp is moved 'Forward or back vtroni the 'locus to spread its light, no eilective portion oit the ilament remains at the focus and substantially none el the emergent rays are pmi'allel to the anis.

lt is the purpose ofmy invention to provide an improved ltype ot lamp capable oli being illumination through 1a range of adj fsted positions. l achieve this purpose by the use oil' an elongated incandescent filament er.- tcnding along the axis ot the retlector. The

invention will described as applied to a` tubular tlashlight, as illustrative oli one of the varied uses to which it may 'lfocusinggf means and associated shoclrabsorbing device illust-rated `in the accompanying 'tocuserh yet giving a satisfactory be put. .The

Serial N'o. 473,217.

drawings are claimed in niycopending application eerial No. 466,639, tiled May 4, 1921. The particular manner of focusing 'l'ornis no part ol? the present invention and any suitable ineens `lor adjust-ing the lamp relative 'to the reflector may be used.

l`he invention will be further described in connccticni with the accompanying drawings,

`in which llig. 1 is a vert-ical section through a tubu-` lar ilashlight embodying my invention, the battery being shown in elevation,

llig. 2 is a vertical transverse section through the flashlight head, showing the novel` iilanrent, Fig. 3 is a diagram i ation oit the device, and

4t and are `side `elevations ot lamp bulbs havii'ig alternative forms of incandescent lilanients. i

ln the drawings reference numeral l indillustrating the oper- -cates a casing of non-conductive material and 2 a battery ot dry cells. A parabolic reflector 3 is retained against the end of casing 1 by a cover glass 1l, which is rigidly held in metal head members 5 and 6. A switch 7 is operable to bridge a gap in contact strips S and 9, respectively in electrical connection with the Zinc bottom of the lowest cell and the reilector 3. The latter is in conductive relation to the exterior terminal of the lamp, but is preferably retained out oil contact with the headinembers 5 and (has shown, so as to prevent accidental short-circuiting through bridging of the exposed metal parts.

The focusing and associated shock absorbing means are illustrated. in Fig. 2. Referring to that ligure, an incandescent lamp 11 is screwed into Ya threaded holder 12, having an outwardly projecting annular flange 13 at its upper end. The reflector 3 is centrally apertured and is provided with a depending tubular portion 14 in which the holder 12 has a sliding lit. The tubular portion 14; is

Vwidened to iliorin van vannular seat 15 for the tlange 13. The unthreaded lower portion 16 oit the tubular lamp holder 12 entends below the base ot the lamp and has an inturned bottoin tlange 17. A hollow cylindrical casing 18 surrounds the tubular holder 12 and has an annular bottom recess 19 shaped to receive the tlange 17. Casing 18 is adapted to telescope upon the widened portion 2O ot the retlector. stein, but is normally held in the retracted position illustrated, by means olf a helical spring 21 which is under compression between the base ofthe casing and the seat on the reflector. Flange 13 aetsas a stop to limit downward movement of theholder 12.

' Coincident pertorations are formed in flange 17 and the base of recess 19. A tubular rivet 22 of conductive material extends through the perfor-ations and is adapted to place the inner terminal of the lamp and the carbon pole of the battery in electrical connection; Rivet 22 is spaced from the holder 12 and casing 18 by rigid discs 23 and 24, of in- Ysulating material, which abut respectively upon the flange 1( and the wall of recess 19. Thev rivet ends 'are expanded or rolled outwardly in the usual manner to secure the di ses and intermediate metal parts firmly together. When the'dises are secured as described, the reflector, holder and casing are held inproper adjustment and may be handled or inserted in the flashlight as a unit. l

By adjusting the end cap 25, the rectilinear filament 26 may be moved forward or back along the axis of the.k reflector with respect to thefocal point 27.v Upward motion of the cap yis transmitted to the battery and through the carbon electrode to the structure carrying the slidable lamp holder 12. 'Ihe moved downwardly,

spring 21 is compressed on upward movement of the holder,and when the end cap 1s permitting the spring f to-expand, it causes the holder tofollow the strong as lwould be too difficultly compressible to yield gated Afilament descending battery,-maintaining the electrical connection between the lamp and carbon electrode. The threaded engagement of the end cap with the casing end holds the parts in vany adjusted position.

VWith the foregoing construction, I can dispense with the spiral spring usually employed in the bottom cap to make contact with the zinc battery terminal. Instead of a spring, a contact making projection 28, having a plane surface in contact with the electrode, isv provided on the bottom of the end cap. f The spring 21, adjacent the lamp, is of 4such strength that in any adjusted position of the spring or inclination of the flashlight it will-have sufficient expansive force to hold the rbattery against the contact making projection 28.v The spring may be made as desired, up to the point where it readily'under impact of the battery.

i The advantageA ofusing an axially eloninstead of one compactly coiled will be apparent fromzfthe diagram,

Vness of illustration and does `filament are taken for' illustration. 4point F coincides Fig. 3, whichfis drawn with a view to clearnotV necessarily 1 vrepresent theA actual proportions of the parts;

Inl-this figure, three points on a rectilinear The with the focus of the para-- f bolic reflector, and the points YF and F lie ofthe focus.

on the axis respectively behind and .in front For the sake of simplicity, rays a concave reflector impinging upon the outermost reflective points P and P only are considered. lhe lines PO and PO are normals drawn to lmcs tangent to the parabolal at l and 1". The rays FP, FP', emerging from the focus are reflected parallel to the axis of the parabola. The rays FI), FP, however, projected from behind the .focal point, have an increased angle of incidence and are therefore caused to diverge outward from the parallel through a distance measured by the increased angle. Similarly, light traversing the paths F1, FP, approaches the normal at a less an le than the focal rays and is bent inward with respect to the parallel rays.

In a properly adjusted lamp, the condition just described obtains and the illumination is of a uniform character. lt may be considered to be made up of a beam of parallel rays emerging from the light source at the focus, and a surrounding envelope of rays produced by the parts of the source adjacent to the focus. In prior adjustable lamps, however, the incandescent filament has been made so short that if' moved any appreciable distance from the locus along the axis of the reflector, in order to spread the beam, substantially noue et the light source remains at the focus. The result is the extinction of the greater portion of' the rays which should be projected parallel to the axis of the reflector and the illumination obtained is characterized by a bright ring surrounding a dull core According to my invention, the incandescent filament is of such length that it may be adjusted to greatly extend the area of illumination without removing all of its effective portions from the focal area. In the diagram, the filament may be considered as extending between points F and F", and in this position is biseeted by the focal point F. Vhen so adjusted, a concentrated beam of maximum intensity is obtained. If the area of illumination is to be increased, the filament is moved forwardly iuto the position FX. It will be noted that a portion of the light source remains at F and parallel rays still emerge from the reflector. In this manner I am able to obtain a greatly enlarged uniformly li hted area. Similar results may be obtame by adjustment of the filament toward the vertex of the reflector.

The essential feature of my invention is the combination with a reflector and focusing device of a lamp having a filament so shaped as to insure adequate illumination in all ndjusted positions. The filament need not be in the form of a straight wire to attain this result. It may for example, have the sha )e shown at 29, Fig. IV, or 30, Fig. V. The invention may be applied also to contours other than parabolic.

I claim A flashlight comprising the combination of laviug a central aperture;

a lamp having an elongated lilainent; an adjustable holder carrying said lamp and movable at will back and fort-h along the axis of said rellector and its aperture; abattery in .3 circuit with said lamp; a tubular casing carnynng;l saidl)alile1y,holder,rellector,lamp and its Vlilalnent in axial alinement; and means on-native at will to adjust said holder, lamp and ite lllalnent along the reflector axis to l0 alter the spread of the reflected light Without opening the circuit including said lamp and battery; said lilanient having a part thereof disposed at the focus of said reflector n every adjusted position of said lamp, whereby light from said :[ilament may be projected at will 15 as a concentrated beam of maximum intensity or as an enlarged diffused beam of uniform intensity.

In testimony whereof, l affix my signature.

LEE J. VOORHEES. 

